Device and method for protecting data in non-volatile memory

ABSTRACT

Disclosed is a non-volatile memory data protecting device and method. The non-volatile memory data protecting device that is used for protecting non-volatile memory data when a power is shut down in a system, may include a signal delay unit to delay a drop in voltage of an input/output line, a power shutdown sensor to sense power shutdown of a system, and a controller to control the signal delay unit in response to whether the system is shut down.

This application is a continuation of application Ser. No. 13/057,034filed on 1 Feb. 2011, which has been issued U.S. Pat. No. 8,446,795, andwhich is the U.S. national phase of International Application No.PCT/KR2009/004304, filed 31 Jul. 2009, which designated the U.S. andclaims priority to KR Application No. 10-2008-0075519, filed 1 Aug.2008, the entire contents of each of which are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a non-volatile memory data protectingdevice and method, and particularly, to a device and method of delayinga drop in voltage of an input/output line for a predetermined time whena power is shut down, such as a system shutdown, thereby protecting datain a non-volatile memory.

BACKGROUND ART

A non-volatile memory, such as a ferroelectric Random Access Memory(FRAM), a magnetoresistive Random Access Memory (MRAM), a phase-changeRandom Access Memory (PRAM), and the like, may access in a byte unit andmay simultaneously maintain contents without a power supply. Thenon-volatile memory has been the focus of attention as a next generationdevice being capable of efficiently compensating a weak point of aconventional Flash memory, and a dynamic Random Access Memory (DRAM)device.

However, although the DRAM device and an SRAM device may temporarilystore unintentional data when a power is abnormally shut down, avolatile device such as the DRAM may not be able to maintain the datawithout the power supply, and thus, the temporarily stored data may bedestructed when the power is cut off. The flash memory device storesdata based on a block unit, and the power of the flash memory device maybe maintained at an threshold voltage level for an appropriate time tostore the data. When the power is abnormally shut down, a time where thepower is maintained at the threshold voltage level is insufficient tostore the data in the flash memory device.

However, the non-volatile memory may store the data during a short timewhere the power is maintained at the threshold voltage level. In thisinstance, all signals transmitted to a memory device are regarded asnormal signals.

When the power is shut down in a system, the power supplied to anon-volatile memory chip slowly decreases due to an effect of acapacitor from a time when the power is shut down. That is, although thepower is cut off, a device is operational until a voltage is less thanor equal to a threshold voltage. Conversely, when the system is shutdown, a memory controller may decrease voltages of all signal linesincluding a chip selection signal, a write enable signal, and the like,to 0V, and thus, data may be inadvertently written in an address number0 of all memory addresses.

Accordingly, there is need for a method of protecting data in anon-volatile memory so as not to destroy data of the non-volatile memorywhen the power is shut down in the system.

DISCLOSURE OF INVENTION Technical Goals

An aspect of the present invention provides a non-volatile memory dataprotecting device and method that may determine whether a power is shutdown in a system, and may delay a drop in voltage of an input/outputline, thereby protecting data of the non-volatile memory fromdestruction even when the power is shut down.

Another aspect of the present invention also provides a non-volatilememory data protecting device and method that may control a delaycircuit, which delays a drop in voltage, to operate only when a power isshut down in a system, thereby preventing a degradation of systemperformance and a malfunction of the system.

Technical Solutions

According to an aspect of the present invention, there is provided anon-volatile memory data protecting device, the device including asignal delay unit to delay a drop in voltage of an input/output line, apower shutdown sensor to sense power shutdown of a system, and acontroller to control the signal delay unit in response to whether thesystem is shut down.

In this instance, the signal delay unit includes at least one of acapacitor, a buffer, and a delay circuit to delay a drop in voltage ofthe input/output line for a predetermined time, and the predeterminedtime is a period where a voltage supplied to the non-volatile memory ischanged to be less than or equal to a threshold voltage.

Also, the power shutdown sensor senses power shutdown by using a digitalsignal that is generated when the power is shut down.

Also, the digital signal includes at least one of a clock enable (CKE)and a power down exit mode.

According to another aspect of the present invention, there is provideda non-volatile memory data protecting method, the method includingsensing power shutdown of a system, and delaying a drop in voltage of aninput/output line in response to the power shutdown of the system.

Also, the sensing of the power shutdown of the system senses the powershutdown by using a digital signal that is generated when the power isshut down.

Also, the delaying of the drop in voltage includes delaying the drop involtage for a predetermined time when the system is shut down by usingat least one of a delay circuit, a buffer, and a capacitor, andpreventing the delay of the drop in voltage when the system is not shutdown.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a memory input signal and a systemvoltage in a conventional system, when a power of the system is shutdown;

FIG. 2 is a diagram illustrating a non-volatile memory data protectingdevice according to an embodiment of the present invention;

FIG. 3 is a flowchart illustrating a non-volatile memory data protectingmethod according to an embodiment of the present invention; and

FIG. 4 is a diagram illustrating a delaying of a signal transfer time byusing a power down exit mode according to an embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The embodiments are described below in order to explain thepresent invention by referring to the figures.

In general, when a non-volatile memory having a same configuration as ageneral memory is used, a board containing a non-volatile memory chipmay have a data line, an address line, and a command line and therebymay perform input/output. In this instance, the address line indicatesan address where input/output is performed. Also, the data line is aroute through which data to be read or written is transmitted, and thecommand line is a channel through which a command to be actuallyexecuted is transmitted. Here, a chip selection signal or a chip enablesignal that indicates a chip to which the command is transmitted and awrite enable signal that indicates a write operation may be transmittedthrough the command line.

FIG. 1 is a diagram illustrating a memory input signal and a systemvoltage in a conventional system, when a power of the system is shutdown.

Referring to FIG. 1, a graph 120 represents that a voltage of the powerof the system decreases when the system is shut down. When the power ofthe system is shut down, a voltage supplied to a non-volatile memorychip slowly decreases due to a capacitor from a time when the power isshut down. That is, although the power is cut off, a device may operateuntil the voltage is less than or equal to a predetermined voltage.Conversely, a graph 110 represents that a memory input signal rapidlydecreases immediately after the system is shut down. That is, when thesystem is shut down, a memory controller may decrease, instantly,voltages of all the signal lines including a chip selection signal, awrite enable signal, and the like, to 0V. Here, when the chip selectionsignal is decreased to 0V, an address number 0 is selected, and when thewrite enable signal is decreased to 0V, data may be written in anaddress number 0 of all memory addresses.

Accordingly, when the system is shut down, existing contents may bedestroyed and the destroyed data may be permanently stored. Sometimes,destruction of contents stored in a corresponding location may cause afateful consequence such as a loss of legal/medical record, a systemoperation error, and the like. Accordingly, there may need for anon-volatile memory data protecting device and method that delays a dropin voltage of a memory input/output line for a predetermined time toprevent existing data from destruction by a new data that is randomlystored in an unintentional location when the system is shut down.Hereinafter, a non-volatile memory data protecting device and methodwill be described in detail.

FIG. 2 is a diagram illustrating a non-volatile memory data protectingdevice according to an embodiment of the present invention.

Referring to FIG. 2, the non-volatile memory data protecting device 200may include a power shutdown sensor 210, a controller 220, and a signaldelay unit 230.

The power shutdown sensor 210 may sense a power shutdown of a system.That is, the power shutdown sensor may monitor the power shutdown of thesystem, such as a system shutdown, and the like, thereby enabling thenon-volatile memory data protecting device 200 to cope with difficultiesoccurring when the power shutdown occurs in the system.

In this instance, the power shutdown sensor 210 may sense the powershutdown by using a digital signal generated when the power is shutdown. Here, the digital signal may include one of a clock enable (CKE)and a power down exit mode. Hereinafter, an example of delaying a signaltransfer time by using the power down exit mode will be described indetail with reference to FIG. 4.

FIG. 4 is a diagram illustrating a delaying of a signal transfer time byusing a power down exit mode according to an embodiment of the presentinvention.

Referring to FIG. 4, a multiplexer 410 may be used to control a signaltransfer route, the multiplexer 410 utilizing the power down exit modeas a selection input 411. In this instance, when the power down exitmode is selected through the selection input 411, a signal may beallowed to detour to a delay circuit 430. That is, a wrong input may beprevented from being inputted to a memory based on a circuit that maydetermine the signal to pass through either a normal circuit 420 or thedelayed circuit 430 according to a status of the power down exit mode.

Referring again to FIG. 2, the signal delay unit 230 may delay a drop involtage of an input/output line. That is, when the power shutdown sensor210 senses the power shutdown, the signal delay unit 230 may delay apoint in time where a memory controller decreases voltages of allinput/output lines including a command line, an address line, a dataline, and the like. In this instance, the delayed time may be set to atime where a voltage supplied to the non-volatile memory 240 is lessthan or equal to a threshold voltage. Here, the voltage supplied to thenon-volatile memory 240 may slowly decrease due to an effect of acapacitor and may operate until the voltage is decreased to be less thanor equal to the threshold voltage, and thus, the signal delay unit 230may delay a time to enable the voltages of all the lines, such as thecommand line, the address line, the data line, and the like, to slowlydecrease. That is, when the voltages of the all lines such as thecommand line, the address line, the data line, and the like, rapidlydecreases, a chip selection signal is decreased to 0V, and thus, anaddress number 0 may be selected. Also, a write enable signal decreasesto 0V, and thus a write is enabled. Also, unintentional data may bestored in an address number 0 of all memory addresses, and thus,existing data may be destroyed. Accordingly, the non-volatile memorydata protecting device 200 may contain the signal delay unit 230 toslowly delay voltages of all lines including the command line, theaddress line, the data line, and the like, thereby delaying the drop involtage for a predetermined time.

In this instance, at least one of a delay circuit, a buffer, and acapacitor may be used to delay the signal transfer time.

Here, the delay circuit or the buffer, which is a nonlinear transfercircuit, may be embodied by using a mono-stable multi-vibrator, a shiftregister, and the like. In this instance, a value inputted to one sideof the shift register is shifted by one bit in an opposite direction ateach clock. After a predetermined number of clocks, the inputted valuemay move to an opposite bit and may appear in an outputting unit. Thatis, the shift register may be used for delaying a signal for apredetermined number of clocks.

Also, when the selection input 411 is in the power exit mode, a CPU or acontroller may generate the write enable signal or the chip selectionsignal after the predetermined number of clocks, to delay the signaltransfer time.

The controller 220 may control the signal delay unit in response towhether the power is shut down in the system. That is, when the power isshut down in the system, the controller may control the signal delayunit to operate and when the power is not shut down in the system, thecontroller may control the signal delay unit to not operate. That is,when the delay circuit, the buffer, and the like are added to thecommand line, the address line, and the data line, generation of acorresponding signal is delayed even in a general operation environment,and thereby may cause a malfunction of the system or a degradation ofsystem performance. Accordingly, the controller 220 may control thesignal delay unit to operate only when the power shutdown sensor 210senses that the power is shut down, to delay the generation or transferof the corresponding signal only when the power is shut down such as asystem shutdown.

As described above, when the power is shut down, the memory controllermay immediately decrease the voltages of all signal lines to 0V, andthus, the delay circuit and the like are contained in the command line,the address line, and the data line to prevent destruction of thenon-volatile memory data, unlike a voltage of non-volatile memory modulethat slowly decreases due to an effect of the capacitor.

Also, the non-volatile memory data protecting device 200 may contain thepower shutdown sensor, thereby preventing a malfunction of the system ora degradation of system performance when a generation or transfer of asignal is delayed even though the power is not shut down.

FIG. 3 is a flowchart illustrating a non-volatile memory data protectingmethod according to an embodiment of the present invention.

Referring to FIG. 3, whether a power is shut down in a system ismonitored and sensed in operations S310 through 320. That is, when thepower shutdown is monitored, preparation is made to prevent datadestruction. In this instance, a digital signal generated when the poweris shut down in the system may be used for determining whether the powerof the system is shut down. Here, the digital signal may include one ofa clock enable (CKE) and a power down exit mode. Also, when the power ofthe system is shut down, a signal delay circuit is enabled to delay asignal to be generated or transferred, the signal delay circuit beingcontained for preventing the data destruction.

In operation S330, when the power is shut down in the system, a timewhere the signal is transferred to a command line, an address line, anda data line may be delayed by using the delay circuit, the buffer, andthe like contained in the system. In this instance, the delayed time mayset a time where a voltage supplied to a non-volatile memory module isdecreased to be less than or equal to a threshold voltage.

That is, a point in time where voltage of the write enable signal isdecreased is delayed to be after a time where the voltage of thenon-volatile memory module is decreased to be less than or equal to thethreshold voltage. Accordingly, even though the voltage of the writeenable signal is 0V and a write enable signal is active, thenon-volatile memory module may not operate since the voltage of thenon-volatile memory module is already decreased to less than or equal to0V. Therefore, the non-volatile memory data protecting device mayprevent destruction of existing data due to random data that is storedin the non-volatile memory after the power shutdown.

As described above, there may be provided a non-volatile memory dataprotecting device and method that may use a delay circuit, a buffer, andthe like until a voltage of a non-volatile memory module is decreased tobe less than or equal to a threshold voltage to delay a signal transfertime, thereby protecting non-volatile memory data from destruction evenwhen a power is shut down.

Also, there may be provided a non-volatile memory data protecting deviceand method that may control a delay circuit, which delays a drop involtage, to operate only when the power is shut down, thereby preventinga malfunction of a system and a degradation of system performance.

The non-volatile memory data protecting method according to theabove-described example embodiments may be recorded in computer-readablemedia including program instructions to implement various operationsembodied by a computer. The media may also include, alone or incombination with the program instructions, data files, data structures,and the like. Examples of computer-readable media include magnetic mediasuch as hard disks, floppy disks, and magnetic tape; optical media suchas CD ROM disks and DVDs; magneto-optical media such as optical disks;and hardware devices that are specially configured to store and performprogram instructions, such as read-only memory (ROM), random accessmemory (RAM), flash memory, and the like. Examples of programinstructions include both machine code, such as produced by a compiler,and files containing higher level code that may be executed by thecomputer using an interpreter.

Although a few embodiments of the present invention have been shown anddescribed, the present invention is not limited to the describedembodiments. Instead, it would be appreciated by those skilled in theart that changes may be made to these embodiments without departing fromthe principles and spirit of the invention, the scope of which isdefined by the claims and their equivalents.

According to an embodiment of the present invention, there may beprovided a non-volatile memory data protecting device and method thatmay determine whether a power is shut down in the system, and may delaya drop in voltage of an input/output line, thereby protecting data ofthe non-volatile memory from destruction even when the power is shutdown.

According to an embodiment of the present invention, there may beprovided a non-volatile memory data protecting device and method thatmay control a delay circuit, which delays a drop in voltage, to operateonly when a power is shut down in a system, thereby preventing adegradation of system performance and a malfunction of the system.

The invention claimed is:
 1. A device for protecting data in anon-volatile memory used in a system, the device comprising: a powershutdown sensor suitable for sensing whether a power of the system isshut down; and a signal delay unit suitable for delaying a drop involtage of a signal to be transferred to the non-volatile memory throughan input/output line when the power of the system is sensed to be shutdown.
 2. The device of claim 1, wherein the power shutdown sensor sensesa power shutdown by using a digital signal that is generated when thesystem is shut down.
 3. The device of claim 1, wherein the signal delayunit includes a normal circuit and a delay circuit, which are selectedbased on the digital signal as a transfer route of the signal.
 4. Thedevice of claim 3, wherein the digital signal includes a power down exitmode signal.
 5. The device of claim 1, wherein the input/output lineincludes a data line, an address line, or a command line.
 6. A devicefor protecting data in a non-volatile memory used in a system, thedevice comprising: a power shutdown sensor to sense a digital signalgenerated when the power of the system is shut down; and a signal delayunit to transfer a signal to an input/output line of the non-volatilememory by passing through a delay circuit delaying a drop in a voltageof the signal according to the digital signal.
 7. The device of claim 6,wherein the input/output line includes at least one of a data line, anaddress line, and a command line.
 8. The device of claim 6, wherein thedelay circuit delays a drop in the voltage of the signal for apredetermined time which is a period where a voltage supplied to thenon-volatile memory is changed to be less than or equal to a thresholdvoltage.
 9. The device of claim 6, further comprising a controller tocontrol the signal delay unit in response to the power shutdown sensorsensing the power shutdown of the system.
 10. The device of claim 9,wherein the controller controls the signal delay unit to operate whenthe power shutdown of the system occurs, and prevents the signal delayunit from operation when the power shutdown of the system has notoccurred.